Diagnostic of cyclogenesis using potential vorticity

摘要

Cyclones and anticyclones are the dominant synoptic scale meteorological systems in midlatitudes. An attractive way to study dynamical aspects of these structures is provided by the use of potential vorticity (PV) framework. In this paper several aspects of midlatitude cyclogenesis are investigated within this PV framework using a case study analysis. The analysis of absolute, relative and potential vorticity implies the significance of the upper level dynamics in the initiation of this case of cyclogenesis. On one hand, the isobaric vorticity analysis appears to be informative, accurate and easy to use as a method for describing the upper-level dynamics. On the other hand the PV analysis provided a summarized picture of the development and the evolution at upper and lower levels, which is directly visible, on the basis of a smaller number of plots compared with the isobaric vorticity analysis. The display of the time sequence of the PV on the appropriate isentropic surface helped in easily understanding the dynamics of the three-dimensional upper level development.